The suspected mastermind behind software which wiped out millions of pounds from its victims around the world may never be arrested due to Russian extradition laws.
Between 500,000 and 1 million machines worldwide were infected with the malicious software, which derived from the original "Zeus" trojan for stealing financial passwords that emerged in 2006.
Russia does not extradite accused criminals to other countries, so hacker Evgeniy Bogachev may never be charged in a US court.
Top FBI official James Cole said: "We are in contact with (Russia) and we've been having discussions with them about moving forward and about trying to get custody of Mr. Bogachev," but he declined to provide further details.
Computer users are constantly being told to change passwords and update software due to the latest "Trojan" or "Bot" - but what are they?
The malware, called GOZeuS is hiding within email attachments, and once downloaded will enable hackers to mine infected computers.